Thermo-electrically controlled latch



April 23, 1957 Filed July 19, 1954 J. R. HOLLlNS THERMO-ELECTRICALLY CONTROLLED LATCH FIG.1

2 Sheets-Sheet 1 I INVENTOR ORNEY Filed July 19, 1954 P 23, 1957 J. R. HOLLINS 2,789,426

THERMO-ELECTRICALLY CONTROLLED LATCH 2 Sheets-Sheet? FIG/5' yd'v kNVENTQR 27 BY a position.

nitcd States Patent TI-IERMO-ELECTRICALLY CONTROLLED LATCH Jesse R. Hollins, Brooklyn, N. Y. Application July 19, 1954, Serial No. 444,215

12 Claims. (Cl. 701-267) This invention relates to electric remote and/or automatically controlled locks or latches and, more particularly, to a simplified lock of this type which is released by electrically energizing a thermo-responsive lock bolt retaining element.

Electrically operated and controlled locks are known which comprise magnetic means for operating, latching and releasing a lock bolt. These locks, while practical in operation, are complicated in construction and require substantial power to operate.

The present invention is directed to an electrically operated or controlled lock in which, when a lock bolt, normally biased to one position, is moved to another position, such as a locked position, an electrically conductive latching element fixed to the lock bolt is automatically releasably engaged by electrically conductive latch means and retained in the operative position. The latch means is continuously biased to the latch release position but is restrained in the latching position by a thermo-responsive retainer, such as a high resistance wire secured between the latch means and a fixed point.

The conductive latching element is electrically connected to one terminal of a source of electric potential. The other terminal of the source is connected to the fixed end of the high resistance wire through a normally open switch. With the lock bolt in operated position, the energizing circuit for the high resistance wire. is complete except for the normally open switch. a

When the switch is closed, current flows through the latch means retainer wire, heating and expanding. the wire. The latch means is thus permitted to move, under its bias, to a latch element releasing position. The released lock bolt is then biased to its first or unoperated The normally open switch may be manually closed or may be closed by a timer or by a special key.

In a modified form of the latch, a time delay may be introduced by connecting a thermostatically operated switch between the high resistance wire fixed point, and the other source terminal. A heatingi circuit for this switch is connected in series with the, latch means and the aforementioned normally open switch When the latter is closed, the heating circuit is energized to heat the thermostatically operated switch. After a preset interval, this latter switch closes the circuit through the resistance wire to release the latch.

For an understanding of the invention, reference is made to the following detailed description of typical embodiments thereof as illustrated in the accompanying drawings. In the drawings:

Fig. 1 is a partial front elevation view of a door and door jamb illustrating one form of the latch;

Fig. 2 is a rear elevation view corresponding to Fig. 1 and schematically illustrating the electrical connections;

another form of latch embodying the invention;

7 Fig. 3 1s a part elevation, and part sectional view of "ice Fig. 4 is a schematic wiring diagram illustrating a timer operated switch controlling the latch; and

Fig. 5 is a scehmatic wiring diagram illustrating a time delay control of the latch.

Referring to Figs. 1 and 2, the invention is illustrated as incorporated in an electrically released latch arrangement generally indicated at 10 in which a bolt 15 is swingably' mounted on a shaft 11 mounted through a door 12. An operating knob 13 is secured to the shaft 11. Bolt 15 is swingable in a generally triangular slot 14 in the free edge of a door 12, and is biased to the retracted position by a tension spring 16. When knob 13 is turned clockwise, bolt 15 enters a suitable keeper on door jamb 17, the keeper being illustrated as an arcuate slot 18 in the edge of jamb 17. In this position, bolt 15 is automatically latched by electrically releasable means to be described.

The inner or back end of shaft 11 has secured thereto a conductive latch element or plate 20. A conductor 21 is schematically illustrated as connecting latch element 20 to a normally open push button 25 connected to one terminal 26 of a suitable source of electric potential. The outer edge of plate 20 has convex cam surfaces 23, 23 intersecting in a notch 24. When knob 13 is turned to move bolt 15 to a locking position, a cam surface 23 of element 20 engages and forces outwardly the bent end 31 of a conductive metal latch means, such as a spring 30, so that end 31 snaps into recess 24 to retain bolt 15 engaged in keeper slot 18.

Spring 30 comprises a bent spring wire anchored to door 12 by pins or screws 32, 33 in such a manner that its free bent end 31 is normally biased outwardly away from latch element or plate 20.

A high resistance wire 35 of Nichrome or the like is connected between spring 30 and a screw or pin 36 on door 12. When cold and contracted, wire 35 pulls spring end 31 inwardly to engage in notch 24 of plate 20. A conductor 37 connects the fixed end of wire 35 to the other terminal 27 of the source of electric potential.

When knob 13 moves bolt 15 to the latching position, engagement of spring end 31 in notch 24 latches bolt 15 in the locking position. At the same time, an electric circuit including wire 35 is completed subject to closure of push button 25.

To release bolt 15, button 25 is depressed so that the circuit is completed. Current flow through Wire 35 heats and expands this wire so that spring end 31 is allowed to move out of notch 24. Spring 16 thereupon snaps bolt 15 to the release position, at the same time breaking the electric circuit.

Fig. 3 illustrates the invention as incorporated in a reciprocating bolt or latch arrangement 10'. Identical elements have been given the same reference characters and corresponding elements have been given the same reference characters primed.

Bolt 15' is reciprocably mounted in guides 41, 42 on door 12, being biased to a retracted position by spring 16. A stop 43 on door 12 engages an abutment 44 on bolt 15 to limit retraction of the latch.

When bolt 15 is projected to enter keeper 18 on door jamb 17, end 31 of spring 30 rides over a cam surface 23 to engage in notch 24, thus locking bolt 15' in the projected or locking position. When push button 25 is closed, bolt 15" is released in the same manner as described for bolt 15 of Figs. 1, and 2.

Fig. 4 schematically illustrates how the latch arrangement may be used as a time lock. In this arrangement, conductor, 21 connects latch element 20 directly to terminal 26. Conductor. 37 connects wire 35. to one of a pair of contacts 46 controlled by a contact elementv 45- operated by a timer 40. The other contact 46 is connected to terminal 27 by a conductor 47. Timer 40 is energized from terminals 26, 27 through a control switch 48.

When bolt 15' is moved to the locking position, it is retained there by engagement of Wire end 31 in notch 24 until such time as timer contact element 45 bridges contacts 46 to complete the heating circuit for wire 35.

In some instances, it may be desirable to delay release of the latch for a pre-set interval following operation of a releasing switch. Fig. shows an arrangement providing such time delay. In this arrangement, conductor 21 connects element 20 directly to terminal 26. Conductor 37 connects wire 35 to a contact 51.

Contact 51 is arranged to be engaged by a thermally responsive conductive metal strip 50 forming part of a thermostatic time delay device generally indicated at 55. One end of strip 50 is anchored in a dielectric mounting 52, and this end is connected to terminal 27 by a conductor 53. When heated, strip 50 bends so that its free end engages contact 51 to connect this contact and wire 35 to terminal 27.

An insulating sleeve 56 is placed on strip 50 and wound with a heating wire 57 electrically connected at one end to spring 30 and thus to wire 35. The other end of wire 57 is connected to terminal 27 through a normally open switch or push button 58.

To release bolt after the latter has been moved to the locking position engaging element with end 31 of spring 30, switch 58 is closed. This completes the following circuit: terminal 26, conductor 21, element 20, spring 30, heating wire 57, switch 58 and terminal 27. Current flowing through wire 57 heats strip 50 so that the latter bends to engage contact 51. Spring 30 is thus connected to terminal 27 through wire 35, conductor 37,

contact 51, strip 50 and conductor 53. Wire 35 thereing from such principles.

What is claimed is: 1. An electrically operated lock bolt mechanism comprising, in combination, a bolt movable between an operated position and a restored position; means biasing said bolt to the restored position; latch means operable to a bolt latching position to releasably retain said bolt in the operated position, said latch means being biased to the bolt releasing position; a thermally expansible electric resistance element connected at one end to said latch 'means and at the other end to a fixed part of the mechanism and effective, when contracted, to constrain said latch means to the bolt latching position and, when expanded, to release said latch means to the bolt releasing position; and means, including a circuit maker and breaker, for applying an electric potential to said expansible element.

2. An electrically operated lock bolt mechanism comprising, in combination, a bolt movable between an op- "erated position and a restored position; means biasing said bolt to the restored position; latch means operable 'to a bolt latching position to releasably retain said bolt in the operated position, said latch means being biased to the bolt releasing position; a thermally expansible electric resistance element connected at one end to said latch means and at the other end to a fixed part of the mech anism and efiective, when contracted, to constrain said -latch means to the bolt latching position and, when expanded, to release said latch means to the bolt releasing position; a normally open circuit maker and breaker; and circuit connections, including means movable with said bolt when moved to the operated position, connecting said circuit maker and breaker to said element to apply an electric potential thereto upon closure of said circuit maker and breaker.

3. A bolt mechanism as claimed in claim 2 in which said element comprises a high resistance wire.

4. A bolt mechanism as claimed in claim 2 in which said circuit maker and breaker comprises a normally open manually operable switch.

5. A bolt mechanism as claimed in claim 2 in which said circuit maker and breaker comprises a normally open timer-operated switch.

6. An electrically operated lock bolt mechanism comprising, in combination, a bolt movable between an operated position and a restored position; means biasing said bolt to the restored position; latch means operable to a bolt latching position to releasably retain said bolt in the operated position, said latch means being biased to the bolt releasing position; a thermally expansible electric resistance element connected at one end to said latch means and at the other end to a fixed part of the mechanism and effective, when contracted, to constrain said latch means to the bolt latching position and, when expanded, to release said latch means to the bolt releasing position; a normally open heating circuit including said element; said normally open heating circuit including a thermostatic device operable, when heated for a pre-sct time, to close said heating circuit; electric heating means for said device; and means, including a circuit maker and breaker, for applying an electric potential to said heating means.

7. An electrically operated lock bolt mechanism comprising, in combination, a. bolt movable between an operated position and a restored position; means biasing said bolt to the restored position; latch means operable to a bolt latching position to releasably retain said bolt in the operated position, said latch means being biased to the bolt releasing position; a thermally expansible electric resistance element connected at one end to said latch means and at the other end to a fixed part of the mechanism and effective, when contracted, to constrain said latch means to the bolt latching position and, when expanded, to release said latch means to the bolt releasing position; a normally open heating circuit including said element and means movable with said bolt when moved to the operated position; said normally open heating circuit including a thermostatic device operable, when heated for a preset time, to close said. heating circuit; electric heating means for said device; and means, including a circuit maker and breaker and said means movable with said bolt when moved to the operated position, for applying an electric potential to said heating means upon closure of said circuit maker and breaker.

8. An electrically operated lock bolt mechanism comprising, in combination, a bolt movable between an operated position and a restored position; means biasing said bolt to the restored position; a conductive metal latch element carried by said bolt; a conductive metal latch spring releasably engageable with said latch element in the operated position of saidbolt; said latch spring being biased to release said latch element; a thermally expansible electric resistance element connected at one end to said latch spring and at the other end to a fixed part of the mechanism and effective, when contracted, to constrain said latch spring to the latch element engaging position and, when expanded, to release said latch spring to the latch element releasing position; and means includ ing a circuit maker and breaker, said latch element and said latch spring for applying an electric potential to said expansible element.

10. A bolt mechanism as claimed in claim 8 in which said circuit maker and breaker comprises a normally open manually operable switch.

11. A bol-t mechanism as claimed in claim 8 in which said circuit maker and breaker comprises a normally open timer-operated switch.

12. -An electrically operated lock bolt mechanism comprising, in combination, a bolt movable between a operated position and a restored position; means biasing said bolt to the restored position; a conductive metal latch element carried by said bolt; a conductive metal latch spring releasably engageable with said latch element in the operated position of said bolt; said latch spring being biased to release said latch element; a thermally expansible electric resistance element connected at one end to said latch spring and at the other end to a fixed part of the mechanism and effective, when contracted, to constrain said latch spring to the latch element engaging position and, when expanded, to release said latch spring to the latch element releasing position; a normally open heating circuit, including said expansible element, said latch element, and said latch spring; a thermostatic de vice operable, when heated for a preset time, to close said heating circuit; electric heating means for said device; and means, including a circuit maker and breaker and said latch element when said bolt is moved to the operated position, for applying an electric potential to said heating means upon closure of said circuit maker and breaker.

No references cited. 

